1. Field of the Invention
The present invention relates to a method of and apparatus of processing a picture signal for conveyance by means of a transmission path or storage medium, in which a
picture signal is subjected to a segmentation algorithm to produce a region signal which identifies edges and closed regions in the picture, and
a texture signal is produced which corresponds to the difference between the picture signal and the region signal.
1. Description of the Prior Art
Such a method of decomposing a picture signal into two components using features identified in the original picture is well known. The two components then can be coded separately. The reasoning behind this approach is that by finding and encoding perceptually important features of the picture they will be preserved and that by the separation of the picture signal into two components of very different character it is possible to design efficient codes for each of them. Image bandwidth compression aims to reduce the amount of information that must be transmitted while simultaneously preserving the quality of the decoded picture.
One problem experienced with the above method is the production of false contours or edges in the region signal in cases where there are gradual changes in the grey level of the picture signal. Here the areas concerned may be separated in the region signal into two or more regions. On reproduction when the decoded region and texture signals are added a disturbance is produced on the display which is seen as a false contour or edge. M. Kocher and R. Leornardi in their paper "Adaptive region growing technique using polynomial functions for image approximation", Signal Processing 11 (1986), pages 47 to 60, Elsevier Science Publishers B.V., propose a method of detecting and overcoming this problem. Basically Kocher and Leornadi propose the generation of a binary control image of the contours in addition to the segmented region signal. This control image is examined for boundary points and a 5.times.5 point (pixel) window centred on each boundary point is examined to establish whether the boundary point is on a true or false contour. If a false contour is established postfiltering is performed within a certain area around the false contour point. The production of an additional contour image signal over and above the region and texture signals for coded transmission increases the amount of processing required at the encoding (transmission) end.